Audio signal processing

Abstract

Systems and methods of processing audio signals are described. The audio signals comprise information about spatial position of a sound source relative to a listener. At least one audio filter generates two filtered signals for each of audio signal. The two filtered signals are mixed with other filtered signals from other audio signals to create a right output audio channel and a left audio output channel, such that the spatial position of the sound source is perceptible from the right and left audio output channels.

What is claimed is: 
     
       1. A method of applying hearing response function approximations to audio signals to reduce spatial localization processing requirements, the method comprising:
 receiving a first audio signal and a second audio signal; 
 filtering the first audio signal with one or more first positional filters, each of the one or more first positional filters configured to approximate a first head-related transfer function (HRTF) by emphasizing first location-relevant portions of the first HRTF by at least applying three or more first component filters to the first audio signal to produce one or more first filtered signals, each of the three or more first component filters configured to contribute to at least a portion of the first location-relevant portions of the first HRTF, the three or more first component filters each selected from the following: a band stop filter, a band pass filter, and a high pass filter; 
 filtering the second audio signal with one or more second positional filters, each of the one or more second positional filters configured to approximate a second head-related transfer function (HRTF) by emphasizing second location-relevant portions of the second HRTF by at least applying three or more second component filters to the second audio signal to produce one or more second filtered signals, each of the three or more second component filters configured to contribute to at least a portion of the second location-relevant portions of the second HRTF, the three or more first component filters each selected from the following: a band stop filter, a band pass filter, and a high pass filter; and 
 combining the one or more first and second filtered signals to produce left and right output signals, such that spatial positions in the left and right output signals are perceptible from left and right speakers. 
 
     
     
       2. The method of  claim 1 , wherein said filtering the first audio signal with one or more first positional filters comprises filtering the first audio signal with two first positional filters and wherein said filtering the second audio signal with one or more second positional filters comprises filtering the second audio signal with two second positional filters. 
     
     
       3. The method of  claim 2 , wherein said combining the one or more first and second filtered signals comprises combining an output of one of the two first positional filters with an output of one of the two second positional filters to produce the left output signal. 
     
     
       4. The method of  claim 2 , wherein said combining the one or more first and second filtered signals comprises combining an output of one of the two first positional filters with an output of one of the two second positional filters to produce the right output signal. 
     
     
       5. The method of  claim 1 , wherein said filtering the first audio signal with one or more first positional filters comprises combining outputs of the three or more first component filters to at least partially produce the one or more first filtered signals. 
     
     
       6. The method of  claim 1 , further comprising filtering a third audio input signal with one or more third positional filters by applying three or more third component filters to at least partially produce a surround output signal. 
     
     
       7. The method of  claim 1 , wherein the first and second HRTFs are the same HRTF. 
     
     
       8. A system for applying hearing response function approximations to audio signals to reduce spatial localization processing requirements, the system comprising:
 one or more first positional filters implemented with one or more processors, each of the one or more first positional filters configured to approximate a first head-related transfer function (HRTF) by emphasizing first location-relevant portions of a first head-related transfer function (HRTF), the one or more first positional filters each comprising three or more first component filters configured to filter the first audio signal to produce one or more first filtered signals, each of the three or more first component filters configured to contribute to at least a portion of the first location-relevant portions of the first HRTF, the three or more first component filters each selected from the following: a band stop filter, a band pass filter, and a high pass filter; 
 one or more second positional filters implemented with the one or more processors, each of the one or more second positional filters configured to approximate a second head-related transfer function (HRTF) by emphasizing second location-relevant portions of a second HRTF, the one or more second positional filters each comprising three or more second component filters configured to filter the second audio signal to produce one or more second filtered signals, each of the three or more second component filters configured to contribute to at least a portion of the second location-relevant portions of the second HRTF, the three or more first component filters each selected from the following: a band stop filter, a band pass filter, and a high pass filter; and 
 a combiner configured to combine the one or more first and second filtered signals to produce left and right output signals, such that spatial positions in the left and right output signals are perceptible from left and right speakers. 
 
     
     
       9. The system of  claim 8 , wherein the one or more first positional filters are further configured to filter the first audio signal with two first positional filters and wherein the one or more second positional filters are further configured to filter the second audio signal with two second positional filters. 
     
     
       10. The system of  claim 9 , wherein the combiner is further configured to combine the one or more first and second filtered signals by at least combining an output of one of the two first positional filters with an output of one of the two second positional filters to produce the left output signal. 
     
     
       11. The system of  claim 9 , wherein the combiner is further configured to combine the one or more first and second filtered signals by at least combining an output of one of the two first positional filters with an output of one of the two second positional filters to produce the right output signal. 
     
     
       12. The system of  claim 8 , wherein the one or more first positional filters are further configured to filter the first audio signal by at least combining outputs of the three or more first component filters to at least partially produce the first filtered signal. 
     
     
       13. The system of  claim 8 , wherein at least some of the first and second component filters are implemented as infinite impulse response (IIR) filters. 
     
     
       14. The system of  claim 8 , wherein the first and second HRTFs are the same HRTF.